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Segment reporting - Narrative (Details) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2020 USD ($) segment | Dec. 31, 2019 USD ($) | Dec. 31, 2018 USD ($)
Segment Reporting Information [Line Items] |  |  |
Number of reportable segments | segment | 2 |  |
Other noninterest expense | $ 213,945 | $ 146,653 | $ 121,200
Relief of goodwill due to sale of TPO mortgage delivery channel | 0 | 100 | 0
Total net contribution reclassification from segment realignment | 82,461 | 109,539 | 105,854
Banking |  |  |
Segment Reporting Information [Line Items] |  |  |
Other noninterest expense | 212,890 | 144,658 | 121,200
Total net contribution reclassification from segment realignment | (20,497) | 99,859 | 100,888
Banking | Segment Realignment, Reclassification, Adjustment |  |  |
Segment Reporting Information [Line Items] |  |  |
Total net contribution reclassification from segment realignment | (26,416) | (7,213) | (3,789)
Mortgage |  |  |
Segment Reporting Information [Line Items] |  |  |
Other noninterest expense | 1,055 | 1,995 | 0
Relief of goodwill due to sale of TPO mortgage delivery channel |  | 100 |
Total net contribution reclassification from segment realignment | 102,958 | 9,680 | 4,966
Interest paid | 14,810 | 11,183 | 16,057
Mortgage | Segment Realignment, Reclassification, Adjustment |  |  |
Segment Reporting Information [Line Items] |  |  |
Total net contribution reclassification from segment realignment | $ 26,416 | $ 7,213 | $ 3,789
Mortgage | Prime Interest Rate |  |  |
Segment Reporting Information [Line Items] |  |  |
Warehouse line of credit interest rate | 3.25% | 4.75% |

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